I. Field of the Invention
This invention relates to a system for setting a conductor pipe assembly in a hole formed in the ocean floor and, in particular, to a method and apparatus for lowering the assembly on a drill string, moving the structure into the hole as it is drilled by the drill string, cementing the structure in the hole, and recovering the drill string.
II. Description of the Prior Art
Underwater exploration and drilling for gas and oil deposits has become increasingly necessary in order to meet rising demands. It has been found that large deposits lie beneath the ocean floors. However, because of current and weather conditions associated with such exploration it is necessary to provide a quick and simple way of setting a conductor pipe assembly from a floating barge or vessel. Until recently, the initial conductor pipe assembly was either jetted into place or driven into the formation. This was possible because of the relatively soft formations, such as sand, within which such wells were drilled. More recently, the formations have been found to be hard enough to require a one-trip, drilled-in conductor pipe system.
One such system is described in U.S. Pat. No. 3,621,910 directed to a method and apparatus for setting an underwater structure. The system described therein requires rotation of the entire drill string in order to commence drilling. In addition, rotation of the drill string is needed in order to latch and unlatch the drill string from the wellhead housing. As a result, the wellhead housing is caused to twist or rotate thereby twisting and tangling the guide lines and hydraulic hoses. Furthermore, this system provided insufficient retraction of the drill string thereby resulting in junking of the well hole in the event the cement inadvertently travels up the interior passageway of the conductor pipe.